1. Field of the Invention
The present invention relates to a lamination type inductor array and more particularly, to a lamination type inductor array to be used as a noise filter or other electronic component in high-frequency electronic circuits and other electronic circuits.
2. Description of the Related Art
One example of such a conventional lamination type inductor array is shown in FIGS. 10 and 11. This lamination type inductor array 15 includes a first insulating sheet 1 having internal conductors 5a-8a disposed on a surface thereof, a second insulating sheet 2 having second internal conductors 5b-8b disposed on a surface thereof, and a protective sheet 3. The linear internal conductors 5a-8a and 5b-8b are arranged so as to extend from and to opposite edges of the sheets 1, 2, respectively.
The sheets 1-3 are stacked on one another, and are integrally baked to define a laminated body 10 as shown in FIG. 11. On the opposite side surfaces of the laminated body 10, external input electrodes 11a-14a and external output electrodes 11b-14b are provided, respectively. The internal conductors 5a and 5b are connected in parallel between the external electrodes 11a and 11b, and define a linear inductor 5. The internal conductors 6a and 6b are connected in parallel between the external electrodes 12a and 12b, and define a linear inductor 6. The internal conductors 7a and 7b are connected in parallel between the external electrodes 13a and 13b, and define a linear inductor 7. The internal conductors 8a and 8b are connected in parallel between the external electrodes 14a and 14b, and define a linear inductor 8.
In the conventional lamination type inductor array 15, the internal conductors 5a, 5b, 6a, 6b, 7a, 7b, 8a, and 8b have the same shape, respectively, and the shape of the inductors 5-8 is the same. When the external dimensions of the laminated body 10 are made smaller so that the inductor array 15 becomes small-sized, the distance d1 (see FIGS. 10 and 11) between the end surfaces in the length direction of the laminated body 10 and the inductors 5 and 8 located adjacent the end surface becomes smaller than the distance d2 between the inductors 5-8.
Because of this fact, the cross section of the magnetic paths which are defined between the inductors 5, 8 on the side of the end surfaces of the laminated body 10 and the end surfaces and along which the magnetic lines of force .phi. of the inductors 5 and 8 pass, becomes smaller. Therefore, the magnetic reluctance of the magnetic paths of the inductors 5 and 8 is increased, and the inductance of the inductors 5 and 8 becomes smaller than that of the inductors 6 and 7.
For example, the actual values at the time when the laminated body 10 has a relative magnetic permeability of 20 is shown in FIG. 13. When the distance d1 is less than 0.5 mm, the inductance of the inductors 5 and 8 on the side of the end surfaces begins to be reduced. When the distance d1 is 0.2 mm, the inductance of the inductors 5 and 8 is about five percent smaller than that of the inner inductors 6 and 7. When the distance d1 is 0.1 mm, the inductance of the inductors 5, 8 is about 13 percent smaller than that of the inductors 6, 7. Even if the sheets 1-3 have a relative magnetic permeability other than 20, the result described above still occurs.
Accordingly, there is a problem with the conventional lamination type inductor array 15 in that the inductance of the inductors 5 and 8 on the side of the end surfaces varies from that of the inner inductors 6 and 7. As a result, dispersion of the electrical characteristics such as noise elimination capability of the inductors 5-8 occurs because of the characteristics which are dependent on the location of the inductors inside the laminated body 10.